The present invention relates to cable and raceway fasteners and, in particular, to a modular, stackable fastener system including retainer straps having serrated prongs that interlock with serrated bores at varieties of base supports, such as nailed base straps, spanner brackets, junction boxes and support bushings.
With increasing labor costs and regulatory requirements for residential and commercial electrical wiring, a need exists for a raceway support system to securely retain and align individual conductors and related multi-conductor conduits to one another. Varieties of disparate, noncompatible fasteners exist, but which are constructed to meet a relatively few, special applications.
Preferably a fastener system should be compatible to a variety of applications, mounting surfaces and conventional wiring devices to permit retrofit use, as well as use within new installations. The system should also be compatible with current installation practices to facilitate acceptance by regulatory authorities, equipment buyers and installers.
Some of the most frequently encountered fasteners used by electricians to secure individual conductors are wire staples. Such staples include nail or screw fasteners which mount through a strap member to a support surface to contain a single conductor bound beneath the strap. The staples are commonly secured to wood and metal frame members and varieties of wall surfaces. Multiple conductors can be contained beneath a single strap, but the straps do not permit a stacked mounting to each other.
Bushings and clamp fasteners also exist for retaining conductors to junction boxes and cabinets at provided "knock-outs". Depending upon the device, screw fastened clamp plates, ribbed wedges and ribbed strap pieces can be used to retain individual conductors to the bored openings. Examples of such devices can be found at U.S. Pat. Nos. 4,892,979; and 3,493,205.
Varieties of conductor retainers have also been integrated into various wiring devices and junction boxes. Depending upon the junction box construction, the retainers may comprise screwed clamps or integral, resilient retainers that cooperate with the box and conductor opening to grip the conductor. Some junction boxes merely provide an opening and rely on an adjacent, separately attached strap fastener (e.g. a wire staple) to secure the conductor to a framing member.
A particular shortcoming of most conventional fasteners is that the fasteners support a single conductor and require horizontal wall space, which space can become limited as the numbers of conductors required in most residential and commercial buildings increase. Unless tightly packed, a potential exists of abrading or piercing such conductors, once covered over during the construction process. Hazards of electrical shocks and fire especially exist for the conductors closest to the edges of a frame member.
In response to the above hazards, cognizant regulatory authorities for wiring devices and practices, such as the National Fire Protection Association have recently revised the National Electric Code to establish code requirements that define specific conductor spacings and positionings with respect to structural framing members. Such regulations inherently limit the available lateral spacings at available framing members. The numbers of potential conductors that can be secured to a framing member are thereby limited, unless redundant intermediate termination points are added.
The present invention was developed in appreciation of the foregoing needs and limitations of existing fasteners and wiring devices used in commercial and residential electrical construction. The fasteners were developed to provide a modular system compatible with existing installation techniques, manufacturing technology and wiring devices and to provide a system of components which can be readily implemented into existing manufacturing processes and use by the installer without undue learning.